Transplants between genetically dissimilar individuals (called xenografts when the doner and host are of different species or allografts when the doner and host are of the same species) normally induce an immune response in the host individual. The immune response often leads to rejection or destruction of the transplant or, if the transplant contains immunocompetent cells, to graft-versus-host disease (GVHD).
Various techniques have been used to attempt to reduce or eliminate the immunogenicity of transplants. For instance, transplants have been manipulated by culturing under conditions that cause selective elimination or deactivation of cells that stimulate the immune response or by treating the transplant with antisera that recognize receptors on such cells. Transplantation Proceedings (1982) 14(4):714-723. Pancreatic islets have also been placed in semipermeable polymeric containers, called "diffusion pouches" in attempts to make an artificial pancreas. Diabetes (1977) 26:1136-9 and Trans Am Soc Artif Intern Organs (1979) 25:74-76.
A series of patents--U.S. Pat. Nos. 4,352,883, 4,391,909, 4,407,957, and 4,409,331--relate to pancreatic islets that are encapsulated in droplet-shaped capsules by initially entrapping the islets in a polysaccharide (e.g., alginate) gel, and then cross-linking the surface of the gel with a polycationic (e.g., polylysine) polymer. Applicant believes that the polysaccharide used in this procedure has no affinity for the islet surface and, indeed, is repelled by the surface of the islets. This increases the likelihood of having holes or gaps in the entrapping gel and failure to encapsulate the islets entirely.
Abst Pap Am Chem Soc (1983) 185:162, Artificial Organs (1984) 8:112, and U.S. Pat. No. 4,353,888 report encapsulation of blood cells in acrylate polymers and suggest the same might be done with other cells such as pancreatic islets.